This invention relates to an electrical musical instrument for semiautomatically producing a series of frequency-related tone signals, such as an arpeggio, and, more particularly, to such an instrument in which production of the related tones is manually controllable through sequential actuation of a set of control switches.
An arpeggio is manually accomplished by a skilled organist by sequentially depressing selected note keys of one octave of the keyboard, followed by the sequential depression of the corresponding keys for the same notes in the next higher octave and so on through the several octaves of the keyboard. This requires the dexterity that is often found lacking except in skilled organists. Accordingly, circuits have been produced for automatically developing an arpeggio effect in which the operator need only depress the keys for the selected notes in one octave and then actuate an arpeggio switch. These circuits, by sequentially enabling logic gates or the like, automatically cause generation of a sequence of arpeggio-related tone signals corresponding to the selected notes. Examples of this type of circuit are shown in U.S. Pat. No. 3,617,602 of Kniepkamp and in the U.S. application of Roman A. Adams, Ser. No. 418,577, filed Nov. 23, 1973, for "Electrical Musical Instrument With Automatic Sequential Tone Generation" now U.S. Pat. No. 3,954,038 assigned to the assignee of the present application. Examples of other automatic arpeggio effect circuits are found in U.S. Pat. Nos. 3,842,184 of Kniepkamp, 3,725,562 of Munch, Jr., et al., 3,718,748 of Bunger, and 3,832,479 of Aliprandi.
While such circuits have effectively enabled unskilled organists to produce an arpeggio effect, the almost complete automatic nature of the tone generation has prevented maximum user satisfaction. Once the notes for the arpeggio have been selected and the arpeggio switch actuated, the circuit takes control. Accordingly, the organist loses a feel of participation in the production of the music.
A proposed solution to this problem is found in the circuit shown in U.S. Pat. No. 3,358,070 of Young. A semi-automatic arpeggio effect circuit is shown in this patent in which keyer circuits are controlled by a set of arpeggio keyboard switches and conventional keyboard switches in such a manner that only when both the arpeggio keyboard switch and a corresponding conventional keyboard switch are closed will a corresponding tone signal be produced. An arpeggio keyboard switch is provided for each selectable note of the several octaves through which the arpeggio is to be developed. Likewise, each arpeggio keyboard switch is connected with the keyer of a tone generator corresponding to its associated note. Selection of a note on the conventional keyboard enables all of the corresponding arpeggio keyboard switches. Actuation of an enabled arpeggio keyboard switch results in generation of the tone signal of the keyer connected therewith. However, note tones are not generated in response to actuation of an arpeggio keyboard switch which has not been enabled.
A semiautomatic arpeggio circuit similar to that of Young is shown in U.S. Pat. No. 3,651,729 of Adachi. There, tone signals are generated through control of a variable frequency oscillator 2. When an operator's finger slides along a resistive rod 8 thereby sequentially engaging it with a plurality of contacts 9, an arpeggio effect is created. The frequency of the oscillator is appropriately changed whenever contact is made with one of the contacts 9 associated with an actuated keyboard switch K1 through K20. As in the circuit of Young, closure of one of the arpeggio control switch contacts 9 results in generation of an appropriate tone only if that switch contact has been enabled through actuation of one of the conventional keyboard switches K1 through K20 associated therewith.
The semiautomatic circuits of Young and Adachi thus overcome the principal disadvantage of the completely automatic arpeggio effect. The aforementioned completely automatic circuits do, however, produce a more perfect arpeggio sequence in which the time period between generation of successive notes is substantially constant and of very short duration. The Young and Adachi circuits produce an arpeggio sequence in which the time periods between immediately successive tone signals vary in accordance with the location of those tone signals on the musical scale, for tone signals are only generated in response to actuation of the arpeggio control switches that are enabled, and no tone signals are produced in response to actuation of the intermediate arpeggio control switches that have not been enabled. For like reasons, the time duration between generation of the last tone signal in one octave and the first tone signal in the next higher octave is dependent upon the note selection, and is variable. In addition, the Young and Adachi circuits require a large number of electrical connections and are, therefore, costly and likely to be subject to failure.